Induced resistance in tomato to whitefly Bemisia tabaci by Bion

Chemical elicitors can induce plant resistance to insects and other pests in susceptible plants. Among them, Benzo [1,2,3] thiadiazole-7-carbothioic acid-S-methyl ester (BTH) is the active ingredient in the Syngenta plant activator Bion. Induced plant resistance to the B and Q biotypes of Bemisa tabaci after foliar application of Bion to cv. Marmande tomato plants was evaluated under controlled conditions.
In a free-choice experiment, adult Q-biotype B. tabaci significantly preferred control plants than plants sprayed with Bion at 0.2 g/l. In consequence, the number of eggs was lower on treated plants, although female fecundity was not affected. After 23 days, a decrease in the number of empty pupal cases was also observed in plants treated with Bion at 0.2 g/l. The effect produced by Bion applied at 0.1 g/l was not significant.
In a no-choice assay, only one leaflet from every tomato plant was treated with 1 g/l Bion or with water (control plants). A clip-cage containing 5 B. tabaci females (biotipe B) was attached to each treated leaflet and to another non-treated leaflet from every plant. After 16 days, the total number of immature insects (eggs+L1+L2) on Bion-treated leaflets was significantly lower than that on water-treated leaflets from control plants. This difference was mostly due to the number of L1 larvae. The acquired resistance seemed to be local (LAR) because of the differences between Bion-treated and non-treated leaflets in the same plants, meanwhile no differences in non-treated leaflets were observed between Bion-treated and control plants.